Not only did Carson not say Trump should stop, he suggested the professional entertainer had a point. And then The Donald himself went on to repeat the widely discredited claim that vaccines cause autism, and nobody called him out.

"CNN was irresponsible to even bring that up," journalist Ana Marie Cox said on HuffPost's "So That Happened" Podcast. "If you even talk about the vaccine debate you give it credence."

During a political dustup over vaccine quackery earlier this year, Cox reported for The Daily Beast that letting childhood immunizations become a polarized political topic could be bad for public health. The problem occurs when people who previously might not have had bad feelings toward immunization begin "to incorporate how they feel about vaccines into their political world view."

On Wednesday night, Trump, Carson and Rand Paul agreed it would be good to slow the schedule of immunizations given to children.

“I’m for vaccines, but I’m also for freedom," Paul said. "Even if the science doesn’t say bunching them up is a problem, I ought to be able to spread my vaccines out a little bit at the very least."

Public health experts and autism advocacy groups do not agree. The American Academy of Pediatrics notes the autism-vaccine link and the supposed benefits of delayed immunizations have been roundly debunked. The Centers for Disease Control and Prevention says delaying children's immunizations just prolongs their vulnerability to potentially lethal illness.

Alison Singer, president and co-founder of the Autism Science Foundation, called the debate over autism dangerous, pointing to the measles outbreak in California this year as an example of what happens when kids don't get their shots.

"This idea that we can space out the vaccines is not grounded in science," Singer said in an interview. "A lot of people don't understand why children get so many vaccines. The reason is we're now able to protect children from so many diseases from which they used to die."

The Autism Self Advocacy Network said in a statement that the focus on vaccines has led to too much research on what causes autism and not enough on autism among adults. The network also said candidates were essentially arguing it would be better to expose children to deadly diseases than autism. "Vaccinations do not cause autism – but the use of autism as a means of scaring parents from safeguarding their children from life-threatening illness demonstrates the depths of prejudice and fear that still surrounds our disability."

This podcast was produced and edited by Adriana Usero and Peter James Callahan, engineered by Brad Shannon, with assistance from Christine Conetta.

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